[page] 264

One thing, above all, remained clear. It was this gradual process of modification-through-blending, supplied through several causes of variation, that he now came to call "natural selection." This is further shown by Darwin's letter to W. R. Greg at the end of 1878, recapitulating the several considerations:

With respect to new variations being obliterated by crossing, I have insisted on the improbability of such well-marked variations as that of the Ancon sheep being preserved under nature. I cannot doubt that the process of selection under nature is the same as that called by me "unconscious selection" when the more or less best fitted are preserved, or the more or less ill-fitted are destroyed. . . . By the way, he (Mivart) says I rest exclusively on natural selection; whereas no one else as far as I know has made so many observations on the effects of use and disuse. Nor do I deny the direct effect of external conditions, tho' I probably underrated their power in the earlier editions of the "Origin"…